Article

How farmers perceive and cope with bowalization: A case study from West Africa

Authors:
  • National University of Agriculture, Republic of Benin
  • Université Nationale d'Agriculture, Bénin
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... The name originates from the fulfulde language in Guinea (Aubréville, 1947). Bowalization occurs when ferricretes are exposed as a result of the erosion of the soil surface by a combination of a dry climate and deforestation (Padonou et al., 2014(Padonou et al., , 2015b. Bowé retain very little water, so any vegetation quickly desiccates and burns early in the dry season. ...
... The natural vegetation of this region is characterized by a mosaic of woodland, dry forest, tree and shrub savanna and gallery forest (Adomou et al., 2006). This zone was selected for study because it is dominated by the ferruginous soils ( Fig. 1) on which bowé occur (Padonou et al., 2014(Padonou et al., , 2015a. Bowé could occur anywhere within the study area. ...
Article
Desertification and land degradation are worldwide problems affecting soil, vegetation and the livelihoods of rural populations. Bowal (plural bowé) is a particular form of degraded land that occurs in tropical regions and leads to the exposure of ferricretes, which are unsuitable for farming. Bowé are more common on farmland and degraded savanna. Changes in land use/land cover were used to map a region of 6.7 million ha in northern) were used to predict the occurrence of bowé in the period up to 2050 using Markovian chain analysis. The results showed a considerable change in land use/land cover during the three periods. The types of land on which bowé occur (farmland and degraded savanna) increased in northern Benin by 5.4% per year during the period 1975–1990 and 9.5% per year during the periods 1990–2010, while the natural vegetation (forest, woodland and tree savanna) decreased by the same amount. The future scenarios also predicted the same trend. In the period 1975–1990, 1.28 million ha (26%) of natural vegetation was converted to degraded savanna and farmland while 2.23 million ha (53%) of natural vegetation was converted to degraded savanna and farmland in the period 1990–2010. Based on the dynamics recorded during the period 1975–1990 and 1990–2010 respectively, a total of 1.28 million ha (26% of the natural vegetation that was present in 1975) and 1.29 million ha (31% of the natural vegetation that was present in 1990) will be converted to farmland and degraded savanna in the study area by 2050.Thus bowalization will persist and increase in the period up to 2050. The natural vegetation could disappear if protection and restoration measures are not taken. It is thus important to take measures to stop the degradation and to implement programs to restore soils on bowé based on the soil and water conservation techniques used on highly degraded West African soils, such as zaï pit and stone rows with grass strips. Some native plants species adapted to bowalization and resistant to climate change in northern Benin (e.g. Asparagus africanus, Andropogon pseudapricus and Combretum nigricans) should be used in association with soil and water conservation techniques on bowé.
... Bowé are characterized by grassland and savanna ( Figure 3) with higher frequency of therophytes than the surrounding savannas and woodlands (Padonou et al., 2014b). Bowalization provokes loss of biodiversity (both plant and animal species) and proliferation of invasive plant species (Padonou et al., 2014a, b). It also leads to local adaptation of plant species an example is Combretum nigricans which develops more stems, more branches and large crown diameter on bowé compare to other soils (Padonou et al., 2012). ...
... Bowalization is perceived by the farmers to be induced by inappropriate land use and soil erosion (Padonou et al., 2014a). Deforestation, bush fires and water erosion are commonly perceived as causes of bowalization in West Africa. ...
Article
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Bowal (plural bowé) is a particular form of degraded land on hardened ferruginous soils (ferricrete) found in tropical regions with unimodal precipitation. It is characterized by ferricrete exposure due to soil surface erosion. The drivers for bowé establishment are deforestation, intensive monocrop production and/or climatic dryness. Bowé are characterized by reduced water retention capacity and electrical conductivity, low organic matter, nitrogen, silt and extractable phosphorus but high amounts of exchangeable potassium and increased soil temperature. Bowalization leads to loss of biodiversity and changes in vegetation structure. The vegetation on bowé is characterized by annual herbaceous plants and trees with impeded roots growth and structural adaptions (e.g Combretum nigricans develops more stems, more branches and larger crown diameter on bowal compared to surrounding soils). Bowalization has negative consequences for crop production. Farmers in West Africa have adopted methods for growing cowpea and groundnut on bowé using a hoe for manual tillage and weed control. Livestock herders exploit the short season with annual grasses and practice transhumance or use food supplies during the dry season. Bowalization is predicted to persist and increase in extent in the future.
... The exposition of ferricrete resulted in bowal expansion (plural bowé) (Aubréville, 1947;Goldman et al., 2011). Bowalization might be human induced (Aubréville, 1947;Goldman et al., 2011;Padonou et al., 2014) or a natural process (André et al., 2003;Thomas et al., 2003). The soil characteristics of bowé impede plant root growth because of absorption of water and burns in dry season. ...
... Thus one could expect change in the spatial distribution of bowé since the climate has becoming more humid particularly in West Africa (Diallo et al., 2012;Diawara et al., 2014). In West Africa, bowé are found in the semiarid and the sub humid climate zone (Padonou et al., 2012(Padonou et al., , 2014Sieglstetter et al., 2012;Zwarg et al., 2012). Hardened ferruginous soils (i.e., ferricretes) could be the only soil types on which bowé occur. ...
... Focus of the study Conceptual framework Empirical data collection Padonou et al. (2014) Perceived causes and consequences of bowalization and coping strategies -Semi-structured household interviews (random sampling) Oyerinde et al. (2015) Adaptation mechanisms to CC, consistency of perceived and observed hydro-climatic trends -Household survey (random sampling) ...
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Understanding coping and adaptation behaviour of different population groups in the context of global environmental change has become increasingly important, especially in regions with high vulnerability such as Sub-Saharan drylands. In this regard, household strategies tend to be dependent on local and context-specific conditions. However, the strategic development of climate change adaptation measures, as well as natural resource and migration management on national and international level require transferable results and recommendations. In this paper, a first attempt is made to address the lack of meta-knowledge and to create a bigger trans-regional picture on the topic. It provides an exploratory and systematic synthesis of quantitative and qualitative data from 63 studies covering more than 9700 rural households from Sub-Saharan African drylands. Relevant household coping and adaptation strategies under different types of environmental change are assessed with a particular focus on the role and relative significance of migration. The results demonstrate that strategies related to crop, livestock, soil and water management are, by far, the most common. Yet, various forms of migration are reported as strategy by about 23% of the households. Corroborated by qualitative findings, this emphasises the importance of migration for responding to unfavourable environmental conditions at the household level. Based on the synthesised literature, future directions for research needed to support socially and ecologically sustainable coping and adaptation are provided.
... Bow e have significantly lower values of electrical conductivity, organic matter, total N, silt and extractable phosphorus than woodland soils but higher amounts of exchangeable potassium (Padonou et al., 2015). The rural population in Benin developed different cropping and livestock breeding techniques to adapt to bowalization (Padonou et al., 2014). ...
Article
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Bowalization is a particular form of land degradation and leads to lateral expansion of ferricrete horizons. The process occurs only in tropical regions. In this study, the most adapted and resistant species towards climate change were identified on bowé. The 15 most common bowé species of the subhumid and semi-arid climate zones of Benin were submitted together with significant environmental variables (elevation, current bioclimatic variables, soil types) to three ecological niche modelling programmes (Maxent, Domain and GARP). For future prediction (2050), IPCC4/CIAT and IPCC5/CMIP5 climate data were applied. Asparagus africanus, Andropogon pseudapricus and Combretum nigricans were identified as the most resistant species for ecological restoration of bowé in the semi-arid climate zone and Asparagus africanus, Detarium microcarpum and Lannea microcarpa in the subhumid climate zone. The ‘Pull’ strategies were identified as appropriate for ecological restoration of bowé in Benin.
... An area with exposed ferricrete (Fig. 1) is called bowal (plural bowé) [4,6,10]. Bowalization can be a natural process [4,28] or human induced [6,10,20]. Bowé retain nearly no moisture [4,10] so the vegetation on bowé desiccates quickly and burns by early fires in the dry season. The soils rapidly absorb and reradiate solar energy, thus during the dry season bowé are extremely hot and barren [10]. ...
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The approaches adopted by local farmers to put the degraded landscape of the Irangi Hills in central Tanzania to productive agricultural use are analysed. The area has been extensively affected by severe soil erosion, thereby reducing its potential for agriculture. While soil erosion in the upper and middle reaches of the slopes has resulted in extensive gullies, sedimentation in the lower reaches has created extensive sandfans and buried some of the fertile, clayey soils.The changes in the present land-use practices were assessed by means of group discussions and transect walks, household interviews, field observations, and by archival research. The results of the study indicate that farmers have responded to the evolving land degradation by using more intensive and more productive forms of land-use. Crops are grown in diverse mixtures, aiming at increasing farm productivity and avoiding the risk of crop failures. Many farmers have also responded to land degradation by employing on-farm conservation practices such as ridge cultivation and tree-planting. There has also been a general shift from cultivation and settlement on hillslopes to less steep, middle and lower pediments and footslope areas.Land-use patterns have constantly changed over the last few decades. One major intervention to try to rehabilitate the worst degraded areas came in 1979, when all livestock were evicted. The quarantine still remains, but since the early 1990s free-grazing livestock have gradually, but illegally, been brought back into the area. Although the return of livestock has increased the availability of manure, it is likely to reverse the trends of ongoing land recovery. To complement the limited availability of animal manure more than 85% of farmers make and use compost to fertilise fields close to homesteads. Evidence is also presented to demonstrate that farmers have been quick to grasp whatever chances they had to make use of new land-use opportunities. When some of the sandfans in the area stabilised, following soil-conservation initiatives, farmers immediately realised that there were new niches in the landscape that could be utilised. Today the total cultivated area has increased considerably, compared to the early 1970s, when intensive conservation efforts were begun.
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Environmental change in the Sahel–Sudan zone of West Africa has been a major issue in development debates over the last decades. Using remote sensing based land cover change analysis, archival data, national and international statistical data, and household interviews, we analyze the drivers of environmental change in Eastern Saloum in Central East Senegal as well as the local perceptions of these changes and adaptation. Being part of the ground nut basin, Eastern Saloum has witnessed rapid environmental degradation caused by the conversion of forest and savanna areas to agricultural land during the last 20–30 years and by a combination of decline in precipitation, soil degradation, a diversity of policies with little concern for the environment, fluctuating markets and population pressure. Farmers perceive the environmental change mainly as land degradation and poor soil fertility, though recent extensification of agriculture counters this effect and has led to increased vegetation cover in marginal areas. They identified erratic climate, agricultural policies, insufficient food production and desire to increase income as the main drivers of change in the area. We conclude that while climate variability has influenced environmental change in the area, various types of State interventions in agriculture and global market fluctuations appear to have been the main underlying causes of environmental degradation.
Article
It is now widely recognized that local farmers possess an important body of knowledge concerning soils and their use for agriculture. This article argues that in order for that knowledge to be useful for sustainable development interventions, it is necessary to go beyond the collection of indigenous soil taxonomies and also explore the theories farmers have on soil formation and degradation processes. Based on field research in eastern Burkina Faso, the article demonstrates that farmers' theories of soil go beyond practical rules of thumb and include complex concepts about soil processes and fertility. In this sense they are similar to scientific theories of soil. It is argued that understanding the similarities and differences in soil related concepts, such as that of soil fertility, could do much more to improve communication between farmers, researchers and development workers than only comparing taxonomies. Furthermore, capturing the grammar (theories) rather than the sentences (taxonomies) provides a much clearer insight to how farmers will deal with changing circumstances and new crops than the static way in which local taxonomies are often treated. Finally, local soil theories are a better point of departure in terms of creating the necessary comprehension of farmer practices required for effective collaboration towards sustainable development.
Article
Soil fertility decline has become a major concern of policy makers worldwide. While many researchers assume that the problem is universal, others question the assumptions, evidence, methodologies and scale upon which beliefs of soil decline are based. Reconciling competing visions of African soils requires a close examination of both farmer perceptions and scientific estimations of change at the local level. This paper discusses local soil knowledge in one small village in southwestern Burkina Faso and relates scientific measures of soil fertility to farmers' perceptions of soil types and changing soil fertility. Farmers' perceptions of soil types and characteristics match up very well with scientific investigations. It is with perceptions of soil degradation that differences occur. While farmers perceive that their soil is degraded, soil analyses show very little change. The goal here is not to argue that one type of knowledge is inherently wrong but to reconcile the two and see how and why differences emerge. Particularly important is a discussion of how contradictions emerge out of the social contexts in which perceptions at the local scale and beyond are embedded.
Article
Groundnut (Arachis hypogaea L.) is the most important oil and cash crop in the sub-Sahelian tropics. Plant adaptation to drought, i.e. cultivars (cvs) that can maintain yield when water is limited, is a complex phenomenon which is not yet fully understood. This study aimed to identify traits expressed at the early stages of the cycle that could reveal cv differences in drought adaptation in the field. The field productivity of four Sahelian groundnut cvs was assessed during three crop seasons in Bambey (Senegal). The same cvs grown in rhizotrons were subjected to early drought stress and to a desiccation test to assess cell membrane tolerance. Between-cv differences were found with respect to pod yield, biomass production, water use efficiency (WUE), stomatal regulation and cell membrane tolerance. Two strategies to cope with water deficit were identified. The first behaviour was characterised by high rapid water loss, late stomatal closure and low cell membrane damage during drought. These traits are all found in the semi-late Virginia cv 57-422 and, into a lesser extent, in the early Spanish cv Fleur 11. For both cvs, biomass production was boosted under favourable conditions in rhizotrons but the semi-late cv had poor pod yield under end-of-season water deficit conditions. The second strategy involved opposite characters, leading to the maintenance of a higher water status, resulting in lower photosynthesis and yield. This characterised the early Spanish cv 73-30, and also, to some extent, the early Spanish cv 55-437. Earliness associated with high WUE, stomatal conductance and cell membrane tolerance, were the main traits of Fleur 11, a cv derived from a Virginia × Spanish cross, which was able to maintain acceptable yield under varying drought patterns in the field. These traits, as they were detectable at an early stage, could therefore be efficiently integrated in groundnut breeding programmes for drought adaptation.
Article
There is a wide range of literature about the relevance of local knowledge, its use and the importance of integrating local knowledge into more formal research settings. Although it is widely recognised that the underlying principles of local and scientific knowledge differ, very little has actually been written about the process of exploring and integrating knowledge sources, particularly the implications of the choice and combination of methodologies and tools used. In this paper, we present our findings from a research project conducted in two villages in Tanzania and two villages in Uganda. The project's objective was to develop methodologies for comparing and integrating scientific and indigenous knowledge of soil and land resources, using Geographical Information System (GIS) as an integration domain. Our focus is on methods and issues in exploring local knowledge of soils. We first give a short overview of the process of exploring local knowledge of soils and the different methodologies used. We present some of the limitations and opportunities that we have encountered during the analysis, arising from the differences in methodologies used and the epistemological differences associated with each knowledge source. The paper highlights the risk that an uncritical approach to local knowledge may lead to misunderstandings and misconceptions that are not apparent until more detailed research is conducted.
Article
The Selva El Ocote Biosphere Reserve is located within the Mesoamerican biodiversity hotspot for global conservation. The area, poorly known relative to other humid tropical areas within Mexico, shows a mosaic of several types of forests, contains over 2000 species of vascular plants and 97 species of mammals, and plays a key role within Mexican tropical forests. We analyze the process of land-use/land-cover change (LUCC) within a 5755 km2 area which includes the reserve. Viability of conservation of the area was assessed by an integrated multi-temporal analysis of the LUCC process. Three cartographical data bases – from 1986, 1995 and 2000 – were used to assess rates and trends in LUCC for seven land cover types: agriculture/pasture (A/P); four types of second-growth forest (SGF); and two types of mature forest (tropical and temperate). Even when taking into account pathways of regeneration, results show a fast net loss of primary and secondary forests, primarily due to the establishment of A/P.For the entire area of study, the annual deforestation rate of tropical mature forests was 1.2% during the period 1986–1995, increasing to 6.8% for the period 1995–2000. For both periods, the annual deforestation rate was appreciably lower within the reserve (0.21% and 2.54%) than outside it (2.15% and 12.4%). The annual rate of conversion of tropical SGF to A/P was 1% during the first period and increased sixfold for the second period. Three future scenarios on forest cover were constructed using a Markovian model and annualizing LUCC transition matrices. Results show that between 29% and 86% of remaining forest may be lost within the next 23 years. Urgent action is necessary to reduce loss of biodiversity within this region. Particular attention must be paid to tropical SGF, which are rapidly being deforested.
Article
Social science analysis has helped to explain the rapid and recent deforestation supposed to have occurred in Guinea, West Africa. A narrative concerning population growth and the breakdown of past authority and community organization which once maintained “original” forest vegetation guides policy. In two cases, vegetation history sharply contradicts the deforestation analysis and thus exposes the assumptions in its supporting social narrative; assumptions stabilized within regional narratives based more on Western imagination than African realities. For each case and then at the regional level, more appropriate assumptions are forwarded which better explain demonstrable vegetation change and provide more appropriate policy guidelines.
Article
We compared the species composition, occurrence and diversity of understorey of forestry plantations and semi-natural secondary forests in a warm-temperate region in southeastern Kyushu, Japan, in which the previous land-use history had been documented. Cluster analysis and a stand ordination, using detrended correspondence analysis, indicated that plant species composition in forest stands was primarily influenced by the previous land-use history (as meadows or coppices) compared with either the current status of the stand (semi-natural forest or plantation) or site micro-topography. Species occurrence was also dependent on the previous land-use, with a significantly greater proportion of native woodland species being present in former coppice stands. Species richness, however, was higher in plantations and stands developing on former meadow sites. This was true of perennial forbs and climbing plants, but not the evergreen species which were originally common in native woodland of the region. Species diversity indices (Shannon’s H′) showed a similar tendency to species richness. The light environment within forest stands, evaluated by gap light intensity (GLI) using hemispherical photography, had less effect on species richness. We conclude that previous land-use has a significant effect on the species composition and diversity of forest, persisting even after the establishment of conifer plantations, and that the restoration of the original ‘woodland’ species composition and diversity will require the retention of efficient seed sources near stands which have developed on land previously cleared of native forest cover.
Article
This research explores the commonalities and differences between local farmers' understanding of soil quality in a small catchment in central Honduras and that of a US soil scientist. The authors investigated the ways in which the local farmers categorized and managed soils and land uses. The US soil scientist also conducted independent measurements and analyses for varying indicators of soil quality throughout the catchment. There were both differences and similarities between the two views of soil quality. Farmers' understanding of soil quality was heavily influenced by the fact that agricultural production was their primary concern, while the soil scientist had a more holistic view of plant productivity. Broader scale movement of soil and water was not a particular concern of the farmers, despite the occurrence of mass wasting and slumping every year. Landform type was a key management variable for both, however, as were soil texture and drainage patterns.
Article
The impacts of climate change, drought and desertification are closely interlinked, and most acutely experienced by populations whose livelihoods depend principally on natural resources. Given the increases in extreme weather events projected to affect the Southern Africa region, it is essential to assess how household and community-level adaptations have been helped or hindered by institutional structures and national policy instruments. In particular, there is a need to reflect on efforts related to the United Nations’ environmental conventions to ensure that policies support the maintenance of local adaptations and help retain the resilience of socio-economic and environmental systems. This paper examines three interlinked drivers of adaptation: climate change, desertification and drought, assessing the extent to which international and national policy supports local adaptive strategies in three countries in southern Africa. We show that while common ground exists between desertification and climate change adaptations at the policy level, they are insufficiently mainstreamed within broader development approaches. Similarly, there are some overlaps between policy-driven and autonomous local adaptations, but the mutually supportive links between them are poorly developed. Further efforts to integrate local adaptation strategies within policy could increase local resilience to environmental change, while also contributing to wider development goals.
Article
Flows on a bajada surface in the Chihuahuan Desert of New Mexico show a discontinuous pattern, with alternating areas of channelization and deposition. Based on their planform appearance, we have termed the depositional areas ‘beads’. Instrumented catchments demonstrated that in comparison to ‘normal’ dendritic catchments, the beads show net infiltration in all but the largest flow events. Net accumulation of the bead surface appears to occur in years of lower than average rainfall, but the surface is dynamic and suffers net erosion in wetter years. The beads have significantly higher total vegetation covers, and contain higher proportions of grass species (Muhlenbergia porteri) as well as the creosotebush that characterizes the bajada surface in general. Creosotebush in the beads show consistently lower values ofδ13 C, suggesting that they are less moisture stressed than creosotebush elsewhere on the bajada. Values of δ15N are higher in the bead creosotebush, suggesting higher rates of soil–nitrogen transformations and greater loss of nitrogen to the atmosphere by denitrification. Both of these factors are again consistent with higher infiltration and thus moisture contents in the beads. In contrast, xylem-pressure potentials in creosotebush in the bead taken before the summer monsoonal season suggest that plants within the bead are more moisture stressed than those outwith the bead. Four possible explanations are offered for this apparent discrepancy: the greater cover and biomass of plants in the bead leads to higher stresses at the end of the drought period; spatial variability in soil texture means that some areas of the bead retain less moisture; more available water in the bead goes to the grass plants that concentrate their roots near the surface; and there is greater competition in the bead during times of drought stress.
Article
Shrub encroachment into grass-dominated biomes is occurring globally due to a variety of anthropogenic activities, but the consequences for carbon (C) inputs, storage and cycling remain unclear. We studied eight North American graminoid-dominated ecosystems invaded by shrubs, from arctic tundra to Atlantic coastal dunes, to quantify patterns and controls of C inputs via aboveground net primary production (ANPP). Across a fourfold range in mean annual precipitation (MAP), a key regulator of ecosystem C input at the continental scale, shrub invasion decreased ANPP in xeric sites, but dramatically increased ANPP (>1000 g m⁻²) at high MAP, where shrub patches maintained extraordinarily high leaf area. Concurrently, the relationship between MAP and ANPP shifted from being nonlinear in grasslands to linear in shrublands. Thus, relatively abrupt (<50 years) shifts in growth form dominance, without changes in resource quantity, can fundamentally alter continental-scale pattern of C inputs and their control by MAP in ways that exceed the direct effects of climate change alone.
Article
Increased soil loss and redistribution are commonly associated with changes in soil structure, yet variability in soil structure in arid ecosystems has been little studied. Soil aggregate stability is a key indicator of soil structure and is correlated with erodibility and water infiltration capacity. In 2000, we compared soil aggregate stability of a complex of Simona (Loamy, mixed, thermic, shallow Typic Paleorthids) and Harrisburg (Coarse-loamy, mixed, thermic, Typic Paleorthids) soils in a Chihuahuan Desert grassland. We examined soil stability at plant and landscape scales by assessing percentage aggregate stability at four sites in two cover classes (plant vs. interspace) located within each of three grass cover and land disturbance classes. To increase measurement sensitivity to changes in soil structure and identify potential early warning indicators for monitoring, we used two different methods for quantifying wet aggregate stability: a laboratory method using a 0.25 mm sieve and a field method using a 1.5 mm sieve. As expected, soil aggregate stability was significantly higher under grass plants than in plant interspaces (44.2 vs. 38.4 for the lab test and 4.4 vs. 3.3 for the field test; P < 0.01). The field test showed higher stability in plots with higher grass cover throughout the top 10 mm soil layer, while disturbance level only affected stability at the soil surface. The laboratory test was insensitive to differences in grass cover and disturbance.
Article
Rangeland degradation, a worldwide problem, is serious in China, especially in the Northern provinces. To assess the pastoralists' perceptions toward rangeland trend and degradation, a survey was conducted in Ningxia, North China. Data were collected from a total of 284 pastoralists in six Ningxia counties. Findings showed that the majority of respondents believe the rangelands in Ningxia have been degraded, although there are some disparities among the counties that illustrate differing severity of degradation. Findings also clarified that the pastoralists have more knowledge about the "technical" and "supportive" aspects of conditions, while remaining less aware of "economic" and "management" factors of this issue. Yet, a high disparity was revealed between pastoralists' perceptions among the counties in this study. The correlation matrix showed that most of their perceptions do not act independently. Findings also showed that those pastoralists who believe that their rangeland trend is "improved" have broader management and social perceptions than those who believe their rangeland is "degraded". Finally, correlation analysis showed that the management and social perceptions have a negative correlation with degradation severity. Based on the findings, recommendations for possible interventions through extension/educational programs to diminish rangeland degradation are made. The programs are suggested to be presented in three packages including "management", "social", and "economic" issues in rangeland degradation.
Article
Thése (1re)--University de Paris. "Extrait de la Revue de géographie physique et de géologie dynamique. Volume xi, fascicule 1, 1938." "Bibliographie": p. 116-120.
Article
A survey was conducted in the Borana pastoral areas of southern Ethiopia to assess current livestock production systems, rangeland management practices and the perceptions of the pastoralists towards rangeland degradation. This information is considered vital to future pastoral development planning and interventions. Data were collected from a total of 20 villages that were identified from 5 peasant associations, namely Did Yabello, Moyatte, Did Harra, Dubuluk and Melbana. The average household size in the study area was 7.23. The majority of the pastoralists relied on both livestock and crop farming. The average livestock holding per household was 14 cattle, 10 goats, 6 sheep and 2 camels. Livestock holdings, with the exception of camels, has shown a declining trend over time. The two most important traditional rangeland management strategies adopted by the pastoralists included burning and mobility, but since 1974/75 burning has no longer been practised. With regard to mobility, the livestock herding falls in two categories, namely: home based and satellite herding. The former involves the herding of milking cows, calves and immature animals (<2 years) close to the encampments. The latter constitutes the herding of bulls and immatures (>2 years) further away from the encampments. Based on the pastoralists' perceptions, the major constraints on livestock production in descending order, were recurrent drought, feed and water scarcity, animal diseases, predators and communal land ownership. All the respondents considered the condition of the rangelands to have declined dramatically over time. In the past most development policies were based on equilibrium theories that opposed the communal use of the rangelands and traditional range management practices. The way in which the pastoral system affects the rangeland ecosystem functioning is contentious to this theory and the 'tragedy of the commons'. There was also a perceived problem of bush encroachment and the ban on traditional burning practices and recurrent droughts were seen as aggravating factors to this invasion process. The increasing practice of crop cultivation on the rangelands was identified as a serious threat to future livestock production and traditional resource management practices. Suggestions for possible interventions to improve the productivity and sustainable use of these rangelands are made.
Cas des départements de l'Alibori et de l'Atakora
  • Au Benin
cotonnière au Benin: Cas des départements de l'Alibori et de l'Atakora. Univer495
SAS/STAT User's Guide. SAS Institute
  • Sas Inc
SAS Inc., 1999. SAS/STAT User's Guide. SAS Institute, Cary, NC. 515
Statistiques théoriques et appliquées. De Boeck et Larcier, Brus- 448 sels
  • P Dagnelie
Dagnelie, P., 1998. Statistiques théoriques et appliquées. De Boeck et Larcier, Brus- 448 sels. 449
Arachis hypogaea L.) cultivars. Environmental and Experimental 439
  • Lian Groundnut
lian groundnut (Arachis hypogaea L.) cultivars. Environmental and Experimental 439
Distribution of vegetation in wind-dominated land504
  • G S Okin
  • D A Gillette
Okin, G.S., Gillette, D.A., 2001. Distribution of vegetation in wind-dominated land504
  • W B Morgan
  • J C Pugh
Morgan, W.B., Pugh, J.C., 1969. West Africa. Methuen, London, pp. 788. 499
Laterization and its control to gold occur533
  • Y Yuangen
  • L Shirong
  • J Zhisheng
Yuangen, Y., Shirong, L., Zhisheng, J., 2009. Laterization and its control to gold occur533
Coton, Magasine trimestriel d'information et de communication de la 421
AIC, 2006. Coton, Magasine trimestriel d'information et de communication de la 421
Analyse des déterminants de l'efficacité de la production 494
  • G S K Midingoyi
Midingoyi, G.S.K., 2008. Analyse des déterminants de l'efficacité de la production 494
Differences in growth and water relation among Phaseo- 442
  • Y Laffray
Y., Laffray, D., 2000. Differences in growth and water relation among Phaseo- 442